Glow 2017 is not based on a true story. It's a work of fiction that was developed for entertainment purposes, drawing inspiration from various sources but not tied to actual happenings.
I think 'glow based on a true story' simply indicates that the entity named 'Glow' has its roots in a factual story. Maybe it's a new business concept that was inspired by how someone overcame difficulties in real life. Or it could be a song that was written because of a real - life love story. The idea is that the essence of 'Glow' comes from something that actually happened.